The Art of War by active 6th century B.C. Sunzi

12. If you are careful of your men,

[Ts’ao Kung says: "Make for fresh water and pasture, where you can turn out your animals to graze."] and camp on hard ground, the army will be free from disease of every kind, [Chang Yu says: "The dryness of the climate will prevent the outbreak of illness."] and this will spell victory.